<meta charset="UTF-8">
<style>
    *{
        padding: 0;
        margin: 0;
    }
    html,body{
        background-color: black;
    }
    .xue{
        width: 200px;
        height: 50px;
        background-color: antiquewhite;
    }
    .xue-life{
        width: 200px;
        height: 50px;
        background-color: brown;
    }
</style>
<body> 
    <div class="xue">
        <div class="xue-life"></div>
    </div>
</body>
<script src="./demo1.js"></script>